Regional variability in the impacts of future land use on summertime temperatures in Kanto region, the Japanese megacityRegional variability in the impacts of future land use on summertime temperatures in Kanto region, the Japanese megacity

Summer high temperatures affecting urban areas pose a significant problem to human health. TheJapanese megacity, Tokyo Metropolitan Area (TMA) in Kanto region, where significant urban shrinkageis expected to occur in the coming decades, is also vulnerable to such temperature issues. We investi-gated the impacts arising from changes in land use on future maximum surface air temperature (Tsmax)at the regional scale in Kanto region. For our numerical experiments, we introduced surface parame-ters (i.e., albedo, evapotranspiration coefficient, and heat capacity) into the Japan Meteorological AgencyNon-Hydrostatic Model (JMANHM), used for operational weather forecasts in Japan. The impacts wereestimated regarding several urban planning scenarios, in which the micro scale afforestation in TMA wasconsidered, i.e., compact-city, dispersed-city, and active afforestation. The obtained results indicated thatthe afforestation might decrease Tsmax, and active afforestation within a compact-city scenario was themost effective for reducing Tsmaxin Kanto region. Our findings also revealed a relatively smaller afforesta-tion impact on Tsmaxvalues in the coastal areas (e.g., Kanagawa) than those affecting inland regions (e.g.,Saitama and Tokyo). In coastal areas located upwind of Kanto region, only local afforestation affectedTsmax. On the other hand, in inland zones, located on the downwind side of Kanto region, afforestation inboth local and upwind areas contributed to a decrease in Tsmax. Consequently, the impacts of afforestationwere larger in inland areas.